1. Field of the Invention
The present invention relates to a high-capacity wire rolling mill including a wire train and/or rod steel train for concrete reinforcing steel and simple carbon steels, further including
a continuous casting plant or a continuous casting wheel for high production, PA1 a direct interconnection of the continuous casting plant or casting wheel to the rolling mill, PA1 a buffer furnace between the continuous casting plant or the casting wheel and the rolling mill for compensating production differences and smaller rolling mill interruptions, PA1 a compact roughing train and intermediate train I, and PA1 a unit calibration for the train sections. PA1 looping by 180.degree. behind the intermediate train I, PA1 an intermediate train II for producing thick finished dimensions or preliminary cross-sections with the possibility of quick stand exchanges, PA1 a finishing train also with the possibility of quick stand exchanges, PA1 the arrangement of the finishing train extending parallel to the intermediate train II, PA1 a common water cooling stretch for and displaceable between the two parallel finishing lines, and PA1 a winding reel arrangement displaceable between the two finishing lines instead of a subsequently arranged equalizing stretch. PA1 replacing the Stelmor conveyor by the winding station; PA1 replacing the cooling bed by the winding station, or PA1 replacing the Garret plant by the winding station.
2. Description of the Related Art
High-capacity wire rolling mills having the above-mentioned features are known in the art. They constitute individual components of a plant concept, however, they are not sufficient for realizing a convincing new concept with respect to the layout for minimized space requirements and investment costs.
In the special print from Klepzik Fachberichte 82 (1974) 11, pages 427/430 with the title "Einadrige Morgan-Siemag-Drahtstra.beta.e", single-strand Morgan-Siemag wore train!, author Heinz Bachmann, schedule basics are described for a new wire train in the Werk Diemlach, Austria, in which, due to very narrow space conditions, a space-saving solution had to be found. Taking into consideration the prevailing local conditions and looking for a plant with the lowest possible investment costs, the only remaining solution was a compact single-strand wire train in a U-shaped configuration. An elongated Morgan train for two-shift operation was used for the heat treatment of the wire. The object was to achieve with a specific heat treatment a wire emerging from a wire train which after cooling had good drawing properties and as uniform as possible a pattern of strength over the entire wire length and over the cross-section of the wire.
A detailed discussion of the problems and the state of the art of water cooling following wire trains can be found in the special print from "DRAHT" 29 (1978) 6, pages 286/89. In that case, as a first stage of a controlled cooling from the rolling heat, usually water cooling is used immediately following the finishing block. Several cooling zones are frequently provided for the wire, wherein the cooling zones cool the wire in stages to the desired placement temperature. Provided between the individual cooling zones are recuperation stretches which have the purpose of making it possible for the wire to equalize its temperature over the cross-section thereof. In conventional cooling stretches which operate with water pressures of between 5 and 15 bars, heat transmission coefficients of up to 50,000 W/m.sup.2 .degree.C. can occur in the region of the nozzle when the rolling speed is about 60 m/sec. Average heat transmission coefficients are about 30,000 to 40,000 W/m.sup.2 .degree.C. When the wire emerges from the cooling stretch, the wire surface is substantially undercooled, while the core of the wire has a remained substantially hotter depending on the cooling intensity and cooling duration. This reference also takes into consideration that significant forces act on the tip of the wire when the wire enters a water-filled pipe, wherein these forces may cause the wire tip to break.
Additional information concerning the heat treatment of steel wire having carbon contents above 0.4% from rolling heat can be found in DE-AS 1 583 411. The invention described in this reference concerns a method of heat treating steel wire from rolling heat, wherein the steel after emerging from the last stand is intermittently superficially quenched and is once again reheated by a temperature equalization with the core cross-section until the pearlite transformation range with an average temperature of 600-665.degree. C. is reached, and the object of this invention is to significantly reduce the previously used substantial length of the cooling stretches at increased rolling speed. In accordance with this reference, this is achieved by cooling the wire surface during quenching intermittently to 70.degree. C. above the martensite transformation temperature, but at least to 400.degree. C., and to subject the wire to intermittent cooling for a period of 0.6 to 0.7 seconds. Quenching takes place in the conventional manner by water cooling and temperature equalization by air cooling.
The special print by "Stahl und Eisen" 108 (1988), Eisenhuttentag, pages 75 to 80 under the title "Temperaturkontrolliertes Walzen von Stabstahl und Draht" temperature-controlled rolling of rod steel and wire!, points out to those skilled in the art that the finish-rolling temperature can be achieved more easily and a better temperature equalization is possible if only one cooling stretch with a long temperature equalization stretch is used. A lowering of the temperature in the finishing train with several cooling stretches, for example, a cooling stretch behind each stand, does not produce the desired result, but increases the length of the plant and is difficult to adjust during practical operation. The reference further mentions that the selected plant arrangement requires that, contrary to the previously used rolling practices, all finished dimensions must be rolled in the two last stands and the stands upstream of the two last stands are not be used when rolling thicker cross-sections. The cooling stretch following the finishing stand has the purpose of reducing the recrystallization in the austenite range, wherein a temperature of about 650.degree. C. is desirable. As a result, the fine granular structure achieved by the transformation is maintained.
Another reference concerning the conception of wire trains with integrated continuous casting plants can be found by those skilled in the art in a translation of the publication from MPT (Verlag Stahl Eisen, Dusseldorf, Germany) Vol. 15 (1992) No. 3, pages 52/58 with the title "Anbindung der Stranggie.beta.anlage an Feinstahl- oder Drahtwalzwerke" interconnection of the continuous casting plant to fine steel or wire rolling mills!by the author U. Svejkovsky. This reference particularly points out the difficulties of a harmonization between the continuous casting plant and the fine steel or wire rolling mill which is due to the fact that these rolling mills have a widely ranging production program with many different dimensions and qualities and small lot sizes. In addition, the various dimensions are rolled in very different quantities because the production quantity is determined very strongly by the rolling speed, especially in the case of small dimensions. This means that the relatively constant continuous casting production cannot be completely sold when rolling small dimensions, while the capacity of the rolling mill is greater in the case of larger finished dimensions.
Described as the best possible solution for these problems has been, inter alia, a heat utilization in accordance with the EHC method (indirect hot charging). In this method, the billets arriving from the continuous casting plant are not directly supplied to the rolling mill furnace, but the thermal energy of the billets is used for heating billets arriving from storage, wherein a heat exchange is carried out in a heating unit. The heating unit is a two-level heat storage unit. In this heat storage unit, cold billet charges which are arriving from storage and are put together in accordance with the rolling schedule are conveyed above the billet charge travelling in the opposite direction and arriving from the continuous casting plant. This causes a heat transfer, preferably by heat radiation.